I managed to get screenshot sharing working on using this plugin: GitHub - PandoraEntertainment/Sharing: A plugin for Unreal Engine 4 that enables Native Sharing.
It has a bug however for versions greater than API 23 (6.0) and after a long time I found how to fix and submitted a pull request for it here:
The creater never merged the pull request however you can do so manaully by changing the parts of the code I changed in the pull request manually.